Use new is*Element() helper functions more in HTML code

Source/core/html/MediaDocument.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 11 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 
 #include "core/html/MediaDocument.h"
 
 #include "HTMLNames.h"
 #include "bindings/v8/ExceptionStatePlaceholder.h"
-#include "core/dom/NodeTraversal.h"
+#include "core/dom/ElementTraversal.h"
 #include "core/dom/RawDataDocumentParser.h"
 #include "core/events/KeyboardEvent.h"
 #include "core/events/ThreadLocalEventNames.h"
 #include "core/frame/LocalFrame.h"
 #include "core/html/HTMLBodyElement.h"
 #include "core/html/HTMLHeadElement.h"
 #include "core/html/HTMLHtmlElement.h"
 #include "core/html/HTMLMetaElement.h"
 #include "core/html/HTMLSourceElement.h"
 #include "core/html/HTMLVideoElement.h"
@@ skipping 79 matching lines @@
 {
     setCompatibilityMode(QuirksMode);
     lockCompatibilityMode();
 }
 
 PassRefPtr<DocumentParser> MediaDocument::createParser()
 {
     return MediaDocumentParser::create(this);
 }
 
-static inline HTMLVideoElement* descendentVideoElement(Node* root)
-{
-    ASSERT(root);
-
-    for (Node* node = root; node; node = NodeTraversal::next(*node, root)) {
-        if (node->hasTagName(videoTag))
-            return toHTMLVideoElement(node);
-    }
-
-    return 0;
-}
-
 void MediaDocument::defaultEventHandler(Event* event)
 {
     Node* targetNode = event->target()->toNode();
     if (!targetNode)
         return;
 
     if (event->type() == EventTypeNames::keydown && event->isKeyboardEvent()) {
-        HTMLVideoElement* video = descendentVideoElement(targetNode);
+        HTMLVideoElement* video = Traversal<HTMLVideoElement>::firstWithin(*targetNode);
         if (!video)
             return;
 
         KeyboardEvent* keyboardEvent = toKeyboardEvent(event);
         if (keyboardEvent->keyIdentifier() == "U+0020" || keyboardEvent->keyCode() == VKEY_MEDIA_PLAY_PAUSE) {
             // space or media key (play/pause)
             if (video->paused()) {
                 if (video->canPlay())
                     video->play();
             } else
                 video->pause();
             event->setDefaultHandled();
         }
     }
 }
 
 }